Compact integrated touch panel display for a handheld device

ABSTRACT

A handheld device with a compact integrated touch panel is disclosed. A handheld device incorporating a touch panel display requiring electrical connections is reduced in size by incorporating electrical pathways within the support structure of the touch panel display, obviating the need for a flex circuit extension from the touch panel display for connection to the handheld device. A further reduction in size is obtained by providing an inherent visually homogeneous perimeter for the touch panel display by matching the colors of the conductive and dielectric materials, thereby eliminating the need for a bezel.

FIELD OF THE INVENTION

The present claimed invention relates to the field of touch paneldisplays. More particularly, the present claimed invention relates totouch panel displays that may be used for handheld devices.

BACKGROUND ART

Over the years, many electronic instruments and devices and beensufficiently reduced in size to become portable, and in turn, smallenough to be held and operated in the hand of the user. The advent ofintegrated circuits greatly increased the number of devices that couldachieve portability and handheld status, as well as increasing thefunctionality of such devices.

Earlier handheld devices such as measuring instruments or electroniccalculators had minimal requirements for display capability and much ofthe available area on the package of the device was dedicated tocontrols such as knobs and buttons, or a keypad. For such instruments, adisplay capable of handling up to a dozen or so alphanumeric characterswas sufficient.

As the information processing capabilities of handheld devices havegrown, the types of information and data that can be displayed thereonhas expanded. For electronic calculators, alphanumeric displays havebeen supplemented by displays that are capable of graphicallyrepresenting mathematical functions.

As handheld calculators acquired more sophisticated displaycapabilities, they have evolved into palmtop computer systems thatprovide text processing and communications applications. Palmtopcomputer systems are commonly used to implement various PersonalInformation Management (PIM) applications such as an address book, adaily organizer, and electronic notepads.

The competing interests of increasing functionality and small size inhandheld devices have led to the adoption of touch panel displays thatprovide a shared surface for input and output functions. Touch paneldisplays are typically multilayer structures combining a transparentmeans of sensing the position and possibly the magnitude of a contactlocal to the display surface with an underlying display.

Most touch panel displays use an electronic means of sensing input;analog-resistive, matrix-resistive, capacitive and near field imaging(NFI) are examples of current technologies. Depending upon thetechnology used, a touch panel may require several distinct electricalconnections to accommodate drive and sense signals to one or moretransparent electrode layers.

Touch panel displays are extremely versatile in that a limitless varietyof “virtual buttons” can be displayed for user input. A palmtop computeremploying a touch panel display can easily modify the areas of thedisplay dedicated to input and output in response to the immediaterequirements of the user and the application. Thus, for handheld devicesthat incorporate a touch panel display, it is desirable to maximize theusable area of the display within the size constraint of being handheld.Further, since not all hands are of the same size, there is a generalrule that smaller is better and this applies to width and length as wellas height. Ideally, the difference in width and length between the touchpanel display and the underlying structure of the handheld device iskept to a minimum.

In spite of the fact that it is desirable to maximize the area availablefor touch panel displays, a portion of the perimeter of typical touchpanel displays used in handheld devices is lost due to the manner inwhich they are integrated into the handheld device.

For instance, a bezel or faceplate is commonly used to hold the touchpanel in place and mask its perimeter. The mechanical function ofsecuring the touch panel in place is relatively straightforward. Thesecond function of a bezel is less than obvious in that its purpose ishidden by design. The sensing portion of touch panel displays typicallyhas a non-transparent electrical structure on its perimeter thatincludes conductive traces and insulation between layers. The geometryand coloration of the conductive and dielectric materials are such thatthey are typically visually non-homogeneous and require masking by thebezel.

Aesthetics aside, it is desirable to have a neutral, homogeneousperimeter surrounding the touch panel display to minimize visualdistraction from the display itself. Due to the limited display size andthe variety of environments in which a handheld device may be used, itis important to give the user every assistance in viewing the display.In typical handheld devices, a bezel achieves the desired homogeneousperimeter by hiding the non-homogeneous pattern beneath it. However, theuse of a bezel dictates an unwanted increase in the overall thickness ofthe handheld device over that which could be obtained for aflush-mounted touch panel display, and may also contribute to anincrease in the length and width as well.

Thus, a need exists for a touch panel display that can be integratedinto a handheld device without requiring a bezel and its associatedincrease in overall device dimensions. There is also a need for a flushmounted touch panel display that presents a visually homogeneous borderto the user without the use of a bezel.

SUMMARY OF INVENTION

Accordingly, several embodiments of the present invention includestructures that enable particular reductions in the overall dimensionsof handheld devices. For example, the elimination of a bezel provides adirect decrease in height of the device. Further, the elimination of thebezel enables a reduction in the width and length of a handheld device.Another embodiment of the invention enables the length or width of thetouch panel display to establish the maximum width and length of theunderlying portion of a handheld device. Another aspect of the inventionenables the aforementioned reductions in dimensions without impairingthe visual characteristics of the touch panel display.

In an embodiment of the present invention, electrical connection betweenthe touch panel display and the remainder of the handheld device isestablished within the projected outline of the touch panel display.That is, when viewed from above, no portion of the handheld deviceextends beyond the perimeter of the touch panel display. For arectangular device, any or all of the four sides may be flush with theedge of the touch panel display.

In another embodiment of the present invention, the entire upper surfaceof the touch panel display is visible and there may or may not be anextension of the remaining portion of the device above the top surfaceof the touch panel display.

In still another embodiment of the invention, distributed localelectrical connections are made between the touch panel display and thehandheld device, thereby minimizing the length of bus traces used on thetouch panel display.

The embodiments described herein enable the reduction in size of ahandheld device having a touch panel display. This reduction in size isachieved by incorporating electrical pathways within the supportstructure of the touch panel display, obviating the need for a flexcircuit extension from the touch panel display for connection to thehandheld device. A further reduction in size is obtained by providing aninherent visually homogeneous perimeter for the touch panel display bymatching the colors of the conductive and dielectric materials, therebyeliminating the need for a bezel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a typical plastic/glass resistive touchpanel.

FIG. 2 shows a top view of a typical trace pattern.

FIG. 3 shows a handheld device with a bezel.

FIG. 4 shows a an exploded view of a typical handheld device assembly

FIG. 5 shows a touch panel with on-film contacts.

FIG. 6 shows a carrier frame with embedded contacts.

FIG. 7 shows a carrier frame with contact block insert.

FIG. 8 illustrates the mounting details for an exemplar embodiment ofthe invention incorporating a resistive touch panel display.

FIG. 9 illustrates the mounting details for an exemplar embodiment ofthe invention incorporating a NFI touch panel display.

FIG. 10 shows a cross-section of a handheld device in accordance withone embodiment of the present claimed invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exploded schematic view of a representative resistive touch screenwith film-on-glass is shown in FIG. 1. A lower contact electrode 10 isseparated from an upper contact electrode 12 by an adhesive dielectricspacer 11. The lower contact electrode 10 is constructed of a glasssubstrate with a transparent conductive coating of indium tin oxide(ITO). The adhesive dielectric spacer 11 serves to bond electrodes 10and 12 together while maintaining electrical isolation between the twoelectrodes. The upper contact electrode 12 is constructed from apolyester film having a transparent conductive ITO coating on its lowersurface as well as a low resistance conductive bus pattern.

A flex circuit tail 13 is attached to the upper contact electrode 12.The flex circuit tail 13 has a plurality of embedded conductors 14. Itshould be noted that the flex circuit tail is a feature common to manytouch panel technologies in addition to the representative resistivetouch panel shown in FIG. 1. Also, a flex circuit tail may contain avarying number of conductors and be attached to more than one electrode.The use of a flex circuit tail is the standard means of establishingelectrical contact for drive and/or sense functions.

The lower contact electrode in FIG. 1 has a conductive trace 15 on itsupper surface that is aligned with a conductive via 16 that traversesthe adhesive dielectric spacer 11. The use of vias in a dielectric layerthat separates opposing electrodes allows external contact to a singleelectrode to distribute signals to both of the opposing electrodes.

The present invention applies to all touch panel displays having anelectrically active transparent element. For purposes of thisdisclosure, an electrically active transparent element is defined as atransparent substrate with a transparent conductive coating that is partof an electronic circuit used to sense input to the touch panel.

FIG. 2 illustrates a bus pattern disposed on the lower surface of theupper contact electrode 12. Traces 21 and 23 provide current to thetransparent conductive ITO coating on one axis, and traces 22 and 24provide current along a second orthogonal axis. The bus pattern istypically printed on the upper contact electrode using a conductive inkconsisting of an organic binder and a metallic filler. Non-transparentconductive inks provide a lower resistance than that obtainable withtransparent conductive coatings, and thus are better suited for buspatterns. Transparent conductive coatings typically have a transmittanceof greater than 80%.

Since most touch panel display technologies have drive and/or sensetraces on at least two opposing edges, an appreciable amount of thedisplay perimeter is subject to visual inhomogeneity.

FIG. 3 illustrates a typical handheld device 30 incorporating a touchpanel display 32 and a bezel 31. FIG. 4 shows an exploded view of thehandheld device of FIG. 3.

In an embodiment of the present invention, the adhesive dielectricspacer 11 shown in FIG. 1 and the bus pattern shown in FIG. 2 areselected such that the visual contrast between the bus pattern and theadhesive dielectric spacer 11 is minimized in the assembled display. Inother words, these objects are made to be the same or similar in color.

The minimization of the visual contrast can be achieved by additives toeither the conductive ink used to print the bus pattern or the adhesivedielectric spacer, or both. The additive may be an organic dye that issoluble in the carrier or binder used in the conductive ink or adhesivedielectric spacer, or it may be a finely divided solid pigment. Forexample, a black dye may be added to the dielectric spacer, and finelydivided carbon may be added to the conductive ink.

The present invention is applicable to any touch screen technology thatincludes at least one transparent substrate having a transparentconductive coating, that requires both electrical connection andisolation at the same surface.

FIG. 5 shows a touch panel substrate similar to that of FIG. 2 butwithout a flex circuit tail. In place of the flex circuit tail there isan array of contact points 50. The array of contact points 50establishes connections to the bus traces on the substrate. A contactpoint 51 establishes contact to a short trace that aligns with a via inan adjacent dielectric spacer (not shown). The construction of the arrayof contact points depends upon the method used to attach the substrateto the remainder of the device and the method for establishingelectrical contact with the contact points. The contact points may beextensions of the bus traces with a particular desired geometry, or theymay formed of an added material such as electroplated metal. Electricalcontact may be established with the array of contact points by adhesiveor by pressure. The array of contact points allows for local electricalcontact with conductors located in the support structure of the touchpanel.

FIG. 6 shows a simple housing 60 including a carrier frame 64 with anupper planar display mounting surface 61 and a floor 65. The housing 60may be of monolithic construction or assembled from a number of parts.The carrier frame 64 is the part of the housing to which the touch paneldisplay is mounted. The carrier frame 64 is preferably made from adielectric material such as a thermosetting resin.

Embedded in one wall of the carrier frame 64 is an array of framecontacts 62. The array of frame contacts may be molded in place, pressfit into a groove, or otherwise embedded. Each frame contact is anelectrical conductor. The upper end of each contact is adapted toestablish contact to a corresponding contact point on touch panelelement such as that shown in FIG. 5.

The upper end of the frame contact may be slightly vertically offsetfrom the planar mounting surface 61. For example, a spring contact or acontact intended for use with particular anisotropic conductiveadhesives would preferably be offset above the planar mounting surface61. The lower end of each contact point is adapted for establishingcontact to a circuit element within the confines of the housing 60.

An example of such an adaptation for establishing contact to a circuitelement is a flying lead 66 comprising a copper wire with a suitablesurface finish for soldering, epoxy bonding, welding, etc. Dependingupon the overall design of the handheld device, there are manyalternatives for establishing contact between the upper surface of theframe contacts and the contact points on the touch panel. For finegeometries, the connection can be made using an anisotropic conductivefilm (ACF) or anisotropic conductive adhesive (ACA) to prevent lateralshort circuits. For coarse geometries, conventional conductive adhesivescan be used in conjunction with non-conducting adhesives to attach atouch panel to the surface 61.

Adhesives for use in sealing to surface 61 include thermoplastic andthermosetting adhesives. Alternatively, a combination of direct heatseal between electrically non-conducting surfaces and electricallyconductive adhesives can be used.

When the use of an adhesive is not required, the frame contacts 62 canbe spring elements that provide electrical contact without bonding.Although the embodiment of FIG. 6 shows a group of frame contactsembedded in one wall, the frame contacts may be distributed over morethan one wall, allowing an effective rerouting of circuit paths on thetouch panel display.

FIG. 7 shows a housing similar to that of FIG. 6, but in this case theframe 70 is fabricated from a conductive material such as aluminum ormagnesium. The array of frame contacts is embedded in a dielectricinsert block 73 which is in turn mounted in the frame 70. The use of adielectric insert block is preferred when a conductive housing is usedor greater precision is desired in the alignment of the frame contacts.

FIG. 8 shows an embodiment of the present invention as applied to afilm-on-glass resistive touch panel display. The upper contact electrode12 extends beyond the adhesive dielectric spacer 11 and the lowercontact electrode 10, allowing the electrical connection to be made tothe frame contact 81. An electrically conductive material 83 is used tobond the upper surface of the frame contact 81 to its correspondingcontact point on the upper contact electrode 12. Further bonding betweenthe touch panel display and the frame is established by the adhesive 84that is disposed in the gap between the touch panel display and the stepfeature of the frame 80. This embodiment is preferred when the uppercontact electrode is very thin and flexible and additional support isdesired.

FIG. 9 shows an embodiment of the present invention incorporating a nearfield imaging (NFI) display. The frame 90 has a protective rim 93 thatserves to shield the edge of the NFI glass substrate 92. The optionalprotective rim 93 provides protection without occluding the display.

FIG. 10 shows a cross-section of a handheld computing device using theframe contact of the present invention. A carrier frame 100 with anintegrated bottom supports a display 102, flex circuit 105 and a touchpanel 101. The display 102 may be a liquid crystal display (LCD), anelectronic paper display, or other suitable display. The flex circuit105 supports and is connected to an integrated circuit 104. The flexcircuit 105 may also be a printed circuit using a rigid substrate. Theflex circuit 105 is also connected to a frame contact 103 by a lead 106.The flex circuit 105 provides electrical connection between theintegrated circuit 104, and the lead 106 and display 102. The framecontact 103 is electrically connected to the touch panel 101. Theintegrated circuit 104 receives input signals from the touch screen 101and outputs drive signals to the display 102. The integrated circuit 104may process the input signals from the display, as well as other inputs,e.g. signals from a probe or communications link connected by means of ajack mounted in the frame 100 (not shown), or an antenna.

The embedded frame contact of the present invention provides increasedflexibility of touch panel bus trace layout since it obviates the needfor a flex circuit tail. When combined with the use of vias throughdielectric spacers, the frame contacts of the present invention can beused to distribute electrical signals to all electrically active layersin a touch panel. The embedded frame contact can be used at any point onthe frame perimeter. Electrical traces that were previously printed ontothe touch panel display can be replaced by the combination of a framecontact and a wire routed in the interior of the housing. Handheldcomputers, test instruments and communications devices are examples ofdevices in which the present invention may be incorporated.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications are suitedto the particular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto and theirequivalents.

1. A handheld device comprising: a touch panel display providing ashared sensing and display surface for input and output functions, saidtouch panel display comprising: a visible adhesive dielectric spacer;and a contact electrode including a transparent conductive coating and avisible non-transparent conductive bus pattern, wherein said visiblenon-transparent conductive bus pattern overlays said visible adhesivedielectric spacer, and wherein said visible non-transparent conductivebus pattern and said visible adhesive dielectric spacer have anapproximately equal visual homogeneous appearance; and a carrier frameto which said touch panel display is mounted, said carrier framecomprising at least one electrically conductive frame contact forestablishing electrical contact with said touch panel display, said atleast one electrically conductive frame contact having an upper end anda lower end; wherein said upper end resides at least in part within atouch panel display mounting surface of said carrier frame and saidlower end is electrically accessible by circuits resident within theconfines of said carrier frame.
 2. The handheld device of claim 1wherein said carrier frame further comprises a dielectric insert block.3. The handheld device of claim 2 wherein said at least one electricallyconductive frame contact comprises a metal.
 4. The handheld device ofclaim 1 wherein said at least one electrically conductive frame contactis press fit into said carrier frame.
 5. The handheld device of claim 1wherein said at least one electrically conductive frame contact ismolded into said carrier frame.
 6. The handheld device of claim 1wherein said at least one electrically conductive frame contact isdistributed over said touch panel display mounting surface.
 7. Ahandheld device comprising a touch panel display providing a sharedsensing and display surface for input and output function, said touchpanel display comprising: a visible adhesive dielectric spacer; and acontact electrode including a transparent conductive coating and avisible non-transparent conductive bus pattern, wherein said visiblenon-transparent conductive bus pattern overlays said visible adhesivedielectric spacer, and wherein said visible non-transparent conductivebus pattern and said adhesive dielectric spacer have an approximatelyequal visual homogeneous appearance.
 8. The handheld device of claim 7further comprising a carrier frame, wherein an electrical contact tosaid touch panel display is established at the interface between themounting surface of said carrier frame and said touch panel display. 9.The handheld device of claim 8 wherein said electrical contact to saidtouch panel display is established using an anisotropic conductive filmor adhesive.
 10. The handheld device of claim 9 wherein said carrierframe further comprises a protective rim.
 11. The handheld device ofclaim 10 wherein said touch panel display is a near field imagingdisplay.
 12. The device of claim 9 wherein said touch panel display is aresistive touch panel display.
 13. The device of claim 12 wherein saidcarrier frame further comprises a protective rim.